1 /*
2 * net/sched/sch_fifo.c The simplest FIFO queue.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; either version
7 * 2 of the License, or (at your option) any later version.
8 *
9 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10 */
11
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/types.h>
15 #include <linux/kernel.h>
16 #include <linux/errno.h>
17 #include <linux/skbuff.h>
18 #include <net/pkt_sched.h>
19
20 /* 1 band FIFO pseudo-"scheduler" */
21
bfifo_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)22 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
23 struct sk_buff **to_free)
24 {
25 if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
26 return qdisc_enqueue_tail(skb, sch);
27
28 return qdisc_drop(skb, sch, to_free);
29 }
30
pfifo_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)31 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
32 struct sk_buff **to_free)
33 {
34 if (likely(sch->q.qlen < sch->limit))
35 return qdisc_enqueue_tail(skb, sch);
36
37 return qdisc_drop(skb, sch, to_free);
38 }
39
pfifo_tail_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)40 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
41 struct sk_buff **to_free)
42 {
43 unsigned int prev_backlog;
44
45 if (likely(sch->q.qlen < sch->limit))
46 return qdisc_enqueue_tail(skb, sch);
47
48 prev_backlog = sch->qstats.backlog;
49 /* queue full, remove one skb to fulfill the limit */
50 __qdisc_queue_drop_head(sch, &sch->q, to_free);
51 qdisc_qstats_drop(sch);
52 qdisc_enqueue_tail(skb, sch);
53
54 qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
55 return NET_XMIT_CN;
56 }
57
fifo_init(struct Qdisc * sch,struct nlattr * opt,struct netlink_ext_ack * extack)58 static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
59 struct netlink_ext_ack *extack)
60 {
61 bool bypass;
62 bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
63
64 if (opt == NULL) {
65 u32 limit = qdisc_dev(sch)->tx_queue_len;
66
67 if (is_bfifo)
68 limit *= psched_mtu(qdisc_dev(sch));
69
70 sch->limit = limit;
71 } else {
72 struct tc_fifo_qopt *ctl = nla_data(opt);
73
74 if (nla_len(opt) < sizeof(*ctl))
75 return -EINVAL;
76
77 sch->limit = ctl->limit;
78 }
79
80 if (is_bfifo)
81 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
82 else
83 bypass = sch->limit >= 1;
84
85 if (bypass)
86 sch->flags |= TCQ_F_CAN_BYPASS;
87 else
88 sch->flags &= ~TCQ_F_CAN_BYPASS;
89 return 0;
90 }
91
fifo_dump(struct Qdisc * sch,struct sk_buff * skb)92 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
93 {
94 struct tc_fifo_qopt opt = { .limit = sch->limit };
95
96 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
97 goto nla_put_failure;
98 return skb->len;
99
100 nla_put_failure:
101 return -1;
102 }
103
104 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
105 .id = "pfifo",
106 .priv_size = 0,
107 .enqueue = pfifo_enqueue,
108 .dequeue = qdisc_dequeue_head,
109 .peek = qdisc_peek_head,
110 .init = fifo_init,
111 .reset = qdisc_reset_queue,
112 .change = fifo_init,
113 .dump = fifo_dump,
114 .owner = THIS_MODULE,
115 };
116 EXPORT_SYMBOL(pfifo_qdisc_ops);
117
118 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
119 .id = "bfifo",
120 .priv_size = 0,
121 .enqueue = bfifo_enqueue,
122 .dequeue = qdisc_dequeue_head,
123 .peek = qdisc_peek_head,
124 .init = fifo_init,
125 .reset = qdisc_reset_queue,
126 .change = fifo_init,
127 .dump = fifo_dump,
128 .owner = THIS_MODULE,
129 };
130 EXPORT_SYMBOL(bfifo_qdisc_ops);
131
132 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
133 .id = "pfifo_head_drop",
134 .priv_size = 0,
135 .enqueue = pfifo_tail_enqueue,
136 .dequeue = qdisc_dequeue_head,
137 .peek = qdisc_peek_head,
138 .init = fifo_init,
139 .reset = qdisc_reset_queue,
140 .change = fifo_init,
141 .dump = fifo_dump,
142 .owner = THIS_MODULE,
143 };
144
145 /* Pass size change message down to embedded FIFO */
fifo_set_limit(struct Qdisc * q,unsigned int limit)146 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
147 {
148 struct nlattr *nla;
149 int ret = -ENOMEM;
150
151 /* Hack to avoid sending change message to non-FIFO */
152 if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
153 return 0;
154
155 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
156 if (nla) {
157 nla->nla_type = RTM_NEWQDISC;
158 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
159 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
160
161 ret = q->ops->change(q, nla, NULL);
162 kfree(nla);
163 }
164 return ret;
165 }
166 EXPORT_SYMBOL(fifo_set_limit);
167
fifo_create_dflt(struct Qdisc * sch,struct Qdisc_ops * ops,unsigned int limit,struct netlink_ext_ack * extack)168 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
169 unsigned int limit,
170 struct netlink_ext_ack *extack)
171 {
172 struct Qdisc *q;
173 int err = -ENOMEM;
174
175 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
176 extack);
177 if (q) {
178 err = fifo_set_limit(q, limit);
179 if (err < 0) {
180 qdisc_destroy(q);
181 q = NULL;
182 }
183 }
184
185 return q ? : ERR_PTR(err);
186 }
187 EXPORT_SYMBOL(fifo_create_dflt);
188
